The importance of peer relationships for children's psychological health and development has been amply demonstrated in previous research. In some studies, acceptance by peers during childhood was the best predictor of mental health or illness in adulthood. Nevertheless, the specific ways in which peer relationships contribute to children's development have not been clearly identified. Several theorists have argued that the most positive effects of interactions with peers occur during early adolescence, when children develop close friendships characterized by equality and intimacy. The major goal of the proposed research is to create and validate procedures for the assessment of intimacy, equality and other features of friendship. The procedures will be used to test previous hypotheses about the development of friendship, to determine whether distinct types of friendships can be identified at a given age, and to examine the processes that lead to equality and intimacy between friends. The methods for the research will include structured observations and open-ended interviews. Friends' interactions will be observed as they work together on a task that allows them either to maintain equaltity by sharing with each other or to compete and try to show their superiority over the other. On a second taks, the friends will engage in discussions that reveal how intimately they understand each other and how close they feel to each other. In the interviews, children will be asked about their friendship with the child with whom they did the tasks. Rather than focusing on a specific feature of friendship, the interviews are designed to provide a general view of a particular friendship from the children's perspective. The proposed research will serve as the foundation for later studies of a child's friendship network, that is, the features of all the child's closest friendships. With measures of the friendship network, it will be possible to directly evaluate hypotheses about the effects of particular types of friendships on children's development. For example, the effects of children's friendships on their adjustment to a new school or their reactions to other life transitions and stresses can be investigated.